German Patent No. 252 205 discloses an atomization device which is suitable for manufacturing thin films by vacuum coating. In particular, it is possible with this device to deposit dielectric films. The atomization device comprises at least two electrodes and magnet systems, the electrodes being electrically connected in such a way that they alternatingly constitute an anode and a cathode. A sine-wave alternating voltage of 50 Hz has proven particularly advantageous. In this device, material ablation occurs from the electrodes in such a way that all the electrodes are ablated uniformly as a result of the alternating voltage.
So-called magnetron sputtering facilities are known to those skilled in the art. They are used, for example, to deposit wear-resistant, metal-containing carbon films. In these, a carbon-containing gas is admitted into a process space or process chamber of the facility, reacted appropriately in the sputtering process on the metal cathode surface being acted upon by a DC voltage, and deposited as a film, together with metal atoms and hydrogen, on the substrates present in the process chamber. The coating plasma which is constituted in the process chamber as a result of the process is located substantially in front of the sputtering cathodes. Because of the large-area cathodes, the coating is highly uniform but also directed. In addition, the coating rate and thus the cost-effectiveness of the method cannot be increased arbitrarily. The coating rate can be increased by adding more of the carbon-containing gas, but this results in the undesirable effect that the surface of the cathodes is increasingly coated in planar fashion with an insulating carbon-containing film. When the surfaces of the cathodes are completely covered, stable DC sputtering operation is no longer possible.
U.S. Pat. No. 3,860,507 discloses a coating method in which two cathodes (targets) located diametrically opposite one another are operated at high frequency (preferably 13.56 MHz), so that a discharge plasma forms between the targets. The targets are connected to two outputs of a secondary coil of an alternating voltage power supply, from which a center tap leads to the wall of the process chamber.
U.S. Pat. No. 5,169,509 furthermore discloses a method in which a reactive coating with electrically insulating films is guaranteed by the fact that two magnetron cathodes are operated with an alternating voltage, while a reactive gas is introduced into the process chamber.